Grad

I have this pump, which is very well-reviewed albeit a bit cheap:
Amazon.com: Schwinn 5-in-1 Floor Pump

When I pump up my tires I will get it to about 85 PSI and then I will release the lever to remove the pump from the valve. When I do that I hear air hiss out and so I quickly try to take it off, but it always takes a second because it kind of sticks. Then I am thinking I deflated the tires too much so I put the pump back on, hear some air hiss while I lock down the adapter, and it reads about 65-70 PSI. So my stupid noob question is this: when I disengage the pump each time am I releasing some air from the tires? If so, should I pump up the tires to a higher PSI than I actually want?

Any other tips on something so incredibly basic that I am kind of embarrassed to ask it on a public forum?

cyclist2000

normally when you release the pump head from the valve you should hear some air hiss. There is compressed air in the hose that is released when the head is taken off the valve.

Grad

Ok, so maybe what is happening is that I hear a hiss when I take it off but no air from the tire is escaping. But then when I put it on again to check the pressure it hisses before I can get it locked into place, and that hiss is air escaping from the tire which is why the pressure has dropped @20 psi?

Wanderer

Possibly correct, so just learn to remove it quicker...... You will always lose a little

Bill Kapaun

A Presta valve should close as soon as any air starts to "backflow" out of the tube.
A Schraeder valve will release air as long as the pin is depressed and the inside pressure is higher than outside.

Any "hiss" when attaching the pump is air lost.

Grad

Ok great, thank you!

radiored

i thank you, too. I was just going to ask the same question, but Grad beat me to it. I notice that my 700X23 tires always read about 80 psi before inflating to 110/105 before a ride. It made me think I was really letting a lot of air out of the Presta valves.

Bill Kapaun

A 23mm tire is going to show a greater pressure loss.
You have minimal volume & relatively high pressure.
Normal "seepage" will have a greater effect (at the same pressure) than a larger volume tire.
It's hard to attach the pump to such a skinny tire without a somewhat noticeable pressure loss. You just have to practice being as quick as you can.

Dyskolos

It's a case of Schrodinger's inner tube. Checking the pressure changes it to an unknown value which is then corrected to a known value which then changes to an unknown value when the pump head is removed. The pressure is both correct and incorrect simultaneously.

My method is to pump to my desired pressure, remove the pump head quickly, give the tire a thump and a squeeze, and not worry further.

jfowler85

When I check my tire pressure, the universe is split into two wherein both possibilities of higher and lower pressure exist.

nfmisso

It is the cat inside the inner tube letting the air out